HIV related opportunistic infections have declined significantly as a result of anti-retroviral therapy. However, other serious medical diseases, such as advanced liver disease, have become an important area of concern in the clinical care of HIV-infected individuals. In this regard, HIV infection is thought to have a negative impact on the progression of liver disease as a result of chronic hepatitis B virus (HBV) infection. Unfortunately, many individuals with HBV disease fail first-line therapy with lamivudine. Adefovir dipivoxil may offer a therapeutic option to HIV- infected individuals who are co-infected with HBV who have failed lamivudine therapy. LIR investigators have recently opened two clinical trials assessing the safety and efficacy of low-dose adefovir (10 mg daily) for the treatment of chronic hepatitis B in HIV-infected individuals who have HBV-related liver disease and persistent HBV plasma viremia despite lamivudine therapy. In addition to evaluating the clinical safety and efficacy of adefovir, we are investigating the impact of HIV infection on HBV-specific cellular immune function. These studies will expand our understanding of the pathogenesis and treatment of HBV disease in HIV-infected people.